To identify the possible problems, you need to use a variety of tools and understand the overall configuration.The following chapters in this guide describe many approaches and specific solutions to potential problems.

Troubleshooting a Switch Crash

When a switch crashes, the cause might be from the failure of a process, and results in a reload of the switch.

A crash is usually recorded with a core file on the switch and includes the reason for the crash, such as a failed process. The following can help you determine the cause of the crash:

Use the show version or show system reset-reason commands to display the reason for the crash.

switch# show system reset-reason

Please look at Note Details

1) At 4054 usecs after Sat Nov 6 15:15:01 2010

Reason: Reset triggered due to HA policy of Reset

Service: clis hap reset

Version: 4.2(1)N2(1)

2) At 841383 usecs after Sat Nov 6 14:56:25 2010

Reason: Reset triggered due to HA policy of Reset

Service: clis hap reset

Version: 4.2(1)N2(1)

Use the show cores command to determine if a core file was recorded. You also can use the show process log command to display the processes and if a core was created.

switch#show process log

Process PID Normal-exit Stack Core Log-create-time

--------------- ------ ----------- ----- ----- ---------------

clis 4023 N Y Y Sat Nov 6 15:14:53 2010

clis 4155 N Y N Sat Nov 6 14:56:18 2010

Use the show processes log details command to provide useful information about the reason for the crash:

switch# show processes log details

Service: clis

Description: CLI Server

Started at Sat Nov 6 14:59:10 2010 (882984 us)

Stopped at Sat Nov 6 15:14:53 2010 (614588 us)

Uptime: 15 minutes 43 seconds

Start type: SRV_OPTION_RESTART_STATELESS (23)

Death reason: SYSMGR_DEATH_REASON_FAILURE_SIGNAL (2)

Last heartbeat 9.35 secs ago

RLIMIT_AS: 687474867

System image name: n5000-uk9.4.2.1.N2.1.bin

System image version: 4.2(1)N2(1) S0

PID: 4023

Exit code: signal 11 (core dumped)

Threads: 4026 4024 4025

Note the module-number and the PID number in the output of the show cores command for the process that crashed. (Usually the module number is 1 for a Nexus 5000 switch.)

switch#show cores

Module-num Instance-num Process-name PID Core-create-time

---------- ------------ ------------ --- ----------------

1 1 clis 4023 Nov 6 15:20

Use the copy core :// module-id / PID ftp : command to export the file and contact the TAC to obtain an analysis of the file.

Obtain the timestamp of the crash with the show version, show system reset-reason, or show cores commands. With the show logging command, review the events that happened just before the crash.

Best Practices

Refer to the release notes for your Cisco SAN-OS release for the latest features, limitations, and caveats.

Enable system message logging.

Troubleshoot any new configuration changes after implementing the change.

Use the Device Manager to manage your configuration and detect possible problems before they become critical.

Common Terms

Term

Description

DCBX

Data Center Bridging Exchange

RSTP+

Rapid Spanning Tree Protocol

FCoE

Fibre Channel over Ethernet

FCF

Fibre Channel Forwarder

FIP

FCoE Initialization Protocol

PFC

Priority Flow Control

ETS

Enhanced Transmission Selection

LLDP

Link Layer Discovery Protocol

CEE

Converged Enhanced Ethernet

VNTag

Virtual Network Tag

Lossless Ethernet

No-Drop Ethernet

CNA

Consolidated Network Adapter

HBA

Host Bus Adapter

NPV/NPIV

N Port Virtualizer

VN-Link

Virtual Network Link

FEX

Fabric Extender

PAA

Port Analyzer Adapter

RCF

Reconfigure Fabric

RSCN

Request State Change Notification

Menlo

Cisco FCoE MUX ASIC

FCP

Fibre Channel Protocol

FSPF

Fabric Shortest Path First

Fabric Manager Tools and CLI Commands

This section highlights the tools and CLI commands that are commonly used to troubleshoot problems. These tools and commands are a portion of what you may use to troubleshoot your specific problem.

The following chapters in this guide may describe additional tools and commands specific to the symptoms and possible problems covered in that chapter.

NX-OS Tips

Displaying what is required from the configuration

switch# show running-config interface

version 4.0(1a)N2(1)

interface vfc29

no shutdown

bind interface Ethernet1/29

interface fc2/3

no shutdown

switchport speed 1000

switchport mode SD

interface fc2/4

interface Ethernet1/1

speed 1000

Displaying within Config Mode

With NX-OS, you can display required data from within the configuration mode, so there is no need to back out to the switch prompt.

switch(config)# show run

switch(config)# show interface brief

Pipe command

switch# show logging |

egrep Egrep

grep Grep

head Stream Editor

last Display last lines

less Stream Editor

no-more Turn-off pagination for command output

sed Stream Editor

wc Count words, lines, characters

begin Begin with the line that matches

count Count number of lines

exclude Exclude lines that match

include Include lines that match

Using the pipe command to only display required keyword

switch# show running-config | include switchport

system default switchport

switchport mode trunk

switchport trunk allowed vlan 1,18

switchport mode fex-fabric

switchport mode fex-fabric

switchport speed 1000

switchport mode SD

no system default switchport shutdown

Copy command

switch# copy ?

bootflash: Select source filesystem

core: Select source filesystem

debug: Select source filesystem

ftp: Select source filesystem

licenses Backup license files

log: Select source filesystem

modflash: Select source filesystem

nvram: Select source filesystem

running-config Copy running configuration to destination

scp: Select source filesystem

sftp: Select source filesystem

startup-config Copy startup configuration to destination

system: Select source filesystem

tftp: Select source filesystem

volatile: Select source filesystem

Redirecting output

NX-OS allows you to redirect outputs to files and flash areas in the switch.

switch# show tech-support aaa > bootflash:ciscolive09

switch# dir

103557265 Apr 01 17:39:22 2009.tmp-system

12451 Apr 10 16:36:37 2009 ciscolive09

49152 Apr 01 17:39:22 2009 lost+found/

20058112 Oct 21 13:10:44 2008 n5000-uk9-kickstart.4.0.0.N1.2.bin

20193280 Apr 01 17:36:37 2009 n5000-uk9-kickstart.4.0.1a.N2.1.bin

76930262 Oct 21 13:11:33 2008 n5000-uk9.4.0.0.N1.2.bin

103557265 Apr 01 17:37:30 2009 n5000-uk9.4.0.1a.N2.1.bin

4096 Jan 01 00:03:26 2005 routing-sw/

Redirecting output of the show tech-support details command

Use the tac-pac filename command to redirect the output of the show tech-support details command to a file and then gzip the file.

The file is stored on bootflash:// filename provided that there is enough memory available. If you do not specify a filename, NX-OS creates the file as volatile:show_tech_out.gz. Copy the file from the device using the procedure in the copy command section.

switch# tac-pac

switch# dir volatile:

374382 Aug 16 17:15:55 2010 show_tech_out.gz

From volatile, copy the file to the bootflash, FTP, or TFTP server.

switch# copy volatile:show_tech_out.gz ?

bootflash: Select destination filesystem

debug: Select destination filesystem

ftp: Select destination filesystem

log: Select destination filesystem

modflash: Select destination filesystem

nvram: Select destination filesystem

running-config Copy from source to running configuration

scp: Select destination filesystem

sftp: Select destination filesystem

startup-config Copy from source to startup configuration

system: Select destination filesystem

tftp: Select destination filesystem

volatile: Select destination filesystem

NX-OS command listing

switch# show cli list | include ?

-i Ignore case difference when comparing strings

-x Print only lines where the match is a whole line

WORD Search for the expression

switch# show cli list | include debug | include interface

Narrowing scope of keywords

You can use many commands like grep and include to narrow the scope of a keyword.

switch(config-if)# show interface | grep fc

fc2/1 is trunking

fc2/2 is trunking

fc2/3 is up

fc2/4 is down (Administratively down)

vfc29 is up

Logging

You can use logging through the CLI or Device Manager. In the following examples, the logging command and the Device Manager display severity information:

Viewing Severity Information with the CLI

switch(config)# show logging

Logging console: enabled (Severity: critical)

Logging monitor: enabled (Severity: notifications)

Logging linecard: enabled (Severity: notifications)

Logging fex: enabled (Severity: notifications)

Logging timestamp: Seconds

Logging server: enabled

{10.91.42.134}

server severity: notifications

server facility: local7

server VRF: management

Logging logflash: disabled

Logging logfile: enabled

Name - ciscolive09: Severity - debugging Size - 4194304

Viewing Severity Levels in the Device Manager

Ethanalyzer and SPAN

Ethanalyzer is a tool that collects frames that are destined to, or originate from, the Nexus 5000 control plane. Node to switch or switch to switch traffic can be seen with this tool.

SPAN is a feature whereby frames that are transient to the switch are copied to a second port for analysis. Node to switch or node to node traffic can be seen via this method.

Ethanalyzer

Ethanalyzer is a Cisco NX-OS protocol analyzer tool based on the Wireshark open source code. This tool is a command-line version of Wireshark that captures and decodes packets. You can use Ethanalyzer to troubleshoot your network and analyze the control-plane traffic.

Command

Description

ethanalyzer local sniff-interface

Captures packets sent or received by the supervisor and provides detailed protocol information.

ethanalyzer local sniff-interface brief

Captures packets sent or received by the supervisor and provides a summary of protocol information.

ethanalyzer local sniff-interface limit-captured-frames

Limits the number of frames to capture.

ethanalyzer local sniff-interface limit-frame-size

Limits the length of the frame to capture.

ethanalyzer local sniff-interface capture-filter

Filters the types of packets to capture.

ethanalyzer local sniff-interface display-filter

Filters the types of captured packets to display.

ethanalyzer local sniff-interface decode-internal

Decodes the internal frame header for Cisco NX-OS.

Note Do not use this option if you plan to analyze the data using Wireshark instead of NX-OS Ethanalyzer.

The following example is for viewing the Spanning Tree Protocol (STP) and Fibre Channel: Using 0 in the command captures output until you press Ctrl-C. The FCID is a well-known name for switch domain controller.

SPAN

The Switched Port Analyzer (SPAN) feature—sometimes called port mirroring or port monitoring—selects network traffic for analysis by a network analyzer. The network analyzer can be a Cisco SwitchProbe, a Fibre Channel Analyzer, or other Remote Monitoring (RMON) probes.

SPAN sources refer to the interfaces from which traffic can be monitored. The Cisco Nexus 5000 Series switch supports Ethernet, virtual Ethernet, Fibre Channel, virtual Fibre Channel, port channels, SAN port channels, VLANs, and VSANs as SPAN sources. With VLANs or VSANs, all supported interfaces in the specified VLAN or VSAN are included as SPAN sources. You can choose the SPAN traffic in the ingress direction, the egress direction, or both directions for Ethernet, virtual Ethernet, Fibre Channel, and virtual Fibre Channel source interfaces:

Ingress source (Rx)—Traffic entering the switch through this source port is copied to the SPAN destination port.

Egress source (Tx)—Traffic exiting the switch through this source port is copied to the SPAN destination port.

Source Ports

A source port, also called a monitored port, is a switched interface that you monitor for network traffic analysis. The switch supports any number of ingress source ports (up to the maximum number of available ports on the switch) and any number of source VLANs or VSANs.

Each source port can be configured with a direction (ingress, egress, or both) to monitor. For VLAN, VSAN, port channel, and SAN port channel sources, the monitored direction can only be ingress and applies to all physical ports in the group. The rx/tx option is not available for VLAN or VSAN SPAN sessions.

Beginning with Cisco NX-OS Release 5.0(2)N1(1). Port channel and SAN port channel interfaces can be configured as ingress or egress source ports.

Source ports can be in the same or different VLANs or VSANs.

For VLAN or VSAN SPAN sources, all active ports in the source VLAN or VSAN are included as source ports.

The Cisco Nexus 5010 switch supports a maximum of two egress SPAN source ports. This limit does not apply to the Cisco Nexus 5020 Switch and the Cisco Nexus 5548 switch.

Characteristics of Destination Ports

Each local SPAN session must have a destination port (also called a monitoring port) that receives a copy of traffic from the source ports, VLANs, or VSANs. A destination port has these characteristics:

Does not participate in spanning tree while the SPAN session is active.

Is excluded from the source list and is not monitored if it belongs to a source VLAN of any SPAN session.

Receives copies of sent and received traffic for all monitored source ports. If a destination port is oversubscribed, it can become congested. This congestion can affect traffic forwarding on one or more of the source ports.

Monitor Caveats

Limitations of Nexus 5000 SPAN CoS values are not preserved at the monitor (span) destination.

Packets coming in on the monitor source with an unknown VLAN tag are spanned ouf with a 0 VLAN tag (priority tag).

For Ethernet destination, the monitor session is up only if the destination port is configured as switch port monitor.

Out of 18 configurable sessions, only two are active (up state). The rest are in down state (hardware resource unavailable).

Failover

FCoE Traffic

When the Nexus 5000 experiences loss of fabric connectivity, it brings down all the affected vFC interfaces.

The following methods are used to signal the host of loss of connectivity to the FC fabric

FIP Clear Link Virtual Link to the CNA will be signaled to indicate the ‘shut’ state of vFC. Throughout the ‘shut’ period FCF Advertisements indicate ‘not available for login’.

In case the loss of connectivity is over the FCoE network, FIP keep-alives are used by the FCF and the CNA to timeout the login sessions. The keep-alive timers are configurable.

Non-FCoE traffic

Under certain failure scenarios where the access switch has lost all uplink connectivity to the aggregation layer, the CNA needs to be signaled of the loss of LAN connectivity. This helps the CNA failover the host traffic to the standby port. Traditionally, such a failure is signaled by bringing down the host facing link. Bringing down the link achieves two purposes:

Host is signaled of loss of connectivity.

The access switch stops forwarding traffic to and from the host-facing link.

However, in the converged network, even though the LAN connectivity is lost at the access switch, the SAN connectivity might still be intact. Bringing down the entire host-facing link is not desirable. Instead, the loss of connectivity is signaled over protocols. Loss of SAN connectivity is signaled using the FIP Clear Virtual Link message. Loss of LAN connectivity is signaled using logical link status TLVs defined in DCBX and VIC protocols.

LAN Traffic

When LAN connectivity is lost for a particular VLAN on the uplinks, the VLAN is also brought down on the host-facing link.

Dedicating a VLAN solely for FCoE traffic helps with shutting down non-FCoE traffic to and from the host-facing link without disrupting FCoE traffic from the same host.